At a time when politicians in both parties have eagerly sought public forums to debate the war in Iraq, Sen. Hillary Rodham Clinton (D-N.Y.) has kept in the shadows.

Clinton has stayed steadfastly on a centrist path, criticizing President Bush but refusing to embrace the early troop withdrawal options that are gaining rapid favor in her party. This careful balance is drawing increasing scorn from liberal activists, frustrated that one of the party's leading lights has shown little appetite to challenge Bush's policy more directly and embrace a plan to set a timetable for bringing U.S. forces home.

Clinton is confronting the Democratic Party's long-standing dilemma on national defense, with those harboring national ambitions caught between the passions of the antiwar left and political concerns that they remain vulnerable to charges of weakness from the Republicans if they embrace the party's base. But some Democrats say, the left not withstanding, her refusal to advocate a speedy exit from Iraq may reflect a more accurate reading of public anxiety about the choices now facing the country.

When Senate Democrats called on President Bush last month to explain the conditions and establish a schedule for withdrawing U.S. forces, Clinton offered backroom advice on the language but let others take the lead on the Senate floor. When Rep. John P. Murtha (D-Pa.) called for removing all U.S. troops from Iraq over the next six months, the New York senator told reporters she was opposed. When her advisers were later asked whether she supports a two-year phased withdrawal advocated by a liberal think tank and embraced by Democratic National Committee Chairman Howard Dean, they demurred.

Faced with rising pressure to join the intensifying debate over an exit strategy and Bush's policies, the politician many think will seek the Democratic Party's presidential nomination in 2008 chose as her medium a 1,600-word letter outlining her views, recently e-mailed to constituents and supporters.

In the e-mail, Clinton took responsibility for her vote for the 2002 resolution authorizing Bush to go to war, while leaving open whether she would have opposed it, given what is now known about faulty intelligence and mismanagement by the administration. She pummeled Bush for his conduct of the war itself but left murky how long she believes U.S. forces should stay in Iraq. As she told Kentucky Democrats earlier this month, "I reject a rigid timetable that the terrorists can exploit, and I reject an open timetable that has no ending attached to it."

Clinton's support for the war continues the pro-defense posture she has maintained in the Senate. As a member of the Armed Services Committee, she has courted Pentagon commanders and military families, and as a senator from New York on Sept. 11, 2001, her advocacy for the campaign against terrorists has been unwavering. But her decision to let others lead the debate over Iraq reflects what allies say is her innate caution.

Antiwar activists have been displeased. "Senator Clinton is demonstrating cowardice in the face of the right-wing noise machine," said Tom Mattzie, Washington director of the liberal group MoveOn.org.

But Clinton's refusal to embrace a quick exit strategy drew strong editorial support from the Buffalo News, which on Thursday praised her as a politician of conviction and conscience.

Some analysts call her approach a classic example of the kind of third-way triangulation -- putting herself at odds not only with the Republicans but also with much of her own party -- practiced by her husband, former president Bill Clinton. Others say she has been on target in her approach. "I think she's been very measured and very thoughtful and very consistent with her criticisms," said Sen. Jack Reed (D-R.I.).

Clinton's support for the war has prompted a challenge from Jonathan Tasini, an antiwar Democrat, in next year's Senate primary in New York. She remains overwhelmingly popular among Democrats in New York, so the challenge may be more an irritant that a real threat. But it could be a harbinger of a more significant challenge from the left to Clinton in 2008, if she decides to seek her party's presidential nomination.

Her advisers say she has adopted positions out of conviction and accepts the consequences of her actions. "She is doing what she believes," said Howard Wolfson, a communications adviser to Clinton. "The politics will either flow from that or they won't."